Stabilization of the spine is often required to correct for trauma, tumor, or degenerative pathologies. Current methods of treatment generally involve the use of a spinal fixation element, such as a relatively rigid fixation rod, that is coupled to adjacent vertebrae by attaching the fixation element to various anchoring devices, such as plates, hooks, bolts, wires, or screws. Spinal stabilization systems, which frequently include two fixation elements disposed on opposite sides of the midline of the spine, hold the vertebrae in a desired spatial relationship, until healing or spinal fusion has taken place, or for some longer period of time.
Due to the intricacies of working in the proximity of the spinal column, such stabilization procedures can result in significant trauma. For example, such procedures typically require that the anchoring devices be implanted into a lateral mass of a target vertebra. In light of this trajectory, significant amounts of muscle and tissue must be stripped from the treatment site due to the relatively large distance between the lateral mass entry point and the midline of the spinal column. Further, any slight miscalculation in the delivery trajectory can result in penetration of a distal portion of the anchoring device (e.g., a pointed tip) into the spinal canal, thereby causing significant injury. As a further disadvantage, the limited bone mass and/or bone density typically found in the lateral mass of a vertebra significantly limits the ability of the vertebra to effectively engage the anchoring devices.
Thus, there remains a need for methods and systems capable of securely positioning fixation assemblies within target vertebrae while also minimizing the risk of injury and associated patient trauma.
When such surgery is performed in the cervical spine, the fixation elements are typically molded according to the anatomy of the skull and the cervical spine, and attached to a fixation plate that is implanted in the occiput. Typically, the occipital plate (e.g., a T-shaped or Y-shaped plate) is positioned along the midline of a patient's occiput such that a single fixation plate can engage spinal fixation elements that run on either side of the midline.
Although each region of the spine presents unique clinical challenges, posterior fixation of the cervical spine is particularly challenging because the anatomy of the cervical spine makes it a technically difficult area to instrument. Specifically, several vital neural and vascular structures, including the vertebral arteries, nerve roots, and spinal cord must be avoided during surgery.
Accordingly, there remains a need for improved spinal fixation devices and methods of improving and/or optimizing cervical stabilization procedures.